Adaptive Subdivision eating RAM incorrectly? Fails all GPU renders regardless of settings
Finally figured out what has been going on.
For some reason Blender is coded to stack the Standard Subdivision settings ONTOP of the Adaptive Subdivision. So if you uncheck Adaptive Subdivision, and have any subdivisions in the Render Subdivision settings, those subdivs are added along with the adaptive ones.
Set original subdivision settings to 0 before checking Adaptive and it seems to work as expected.
This definitely does not feel intended, and is super unclear for the user.
Hope this helps someone else.